// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_BASE_UNIQUE_NOTIFIER_H_
#define CC_BASE_UNIQUE_NOTIFIER_H_

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "cc/base/cc_export.h"

namespace base {
class SequencedTaskRunner;
} // namespace base

namespace cc {

class CC_EXPORT UniqueNotifier {
public:
    // Configure this notifier to issue the |closure| notification when scheduled.
    UniqueNotifier(base::SequencedTaskRunner* task_runner,
        const base::Closure& closure);

    // Destroying the notifier will ensure that no further notifications will
    // happen from this class.
    ~UniqueNotifier();

    // Schedule a notification to be run. If another notification is already
    // pending, then only one notification will take place.
    void Schedule();

    // Cancel a pending notification, if one was scheduled.
    void Cancel();

private:
    void Notify();

    // TODO(dcheng): How come this doesn't need to hold a ref to the task runner?
    base::SequencedTaskRunner* const task_runner_;
    const base::Closure closure_;

    // Lock should be held before modifying |notification_pending_|.
    base::Lock lock_;
    bool notification_pending_;

    base::WeakPtrFactory<UniqueNotifier> weak_ptr_factory_;

    DISALLOW_COPY_AND_ASSIGN(UniqueNotifier);
};

} // namespace cc

#endif // CC_BASE_UNIQUE_NOTIFIER_H_
